How to edit normals so light is even all the way around for grass patches?
For this case you need to select "Directional" and "Parallel Normals". The vector from your object origin to the target object origin is set as the normal for each of the vertices.



For grass usage case I would recommend trying a normal that points straight up as this is unaffected by rotation around Blender Z / Unity Y axis. But please note that this will make the faces' shaded color identical so the only difference in color will come from albedo / diffuse texture.